The present invention relates to a rotation stabilizing device deterring rotation fluctuation and thereby stabilizing the rotation, a rotation driving mechanism equipped with the rotation stabilizing device, and to an image forming apparatus and an image reading apparatus which can deter rotation fluctuation in an image carrier such as a photoreceptor drum.
In recent years, there are demands for the technology to stabilize driving in various technical fields. For example, in an image forming apparatus such as a copying machine, a developing agent, namely, toner is used for developing a latent image on a photoreceptor drum representing an image carrier. In general, toner is a powdery substance having a size of about 10 xcexcm, and it is structured with resin and a magnetic substance, or with resin and an adhesive agent.
When forming an image, toner is adsorbed on a photoreceptor drum on which electric charges are accumulated, then, the toner is transferred onto paper representing an image forming object, and this toner is fixed on the paper by the use of a fixing roller. Toner which failed to be transferred and is remaining on a photoreceptor drum is removed from the photoreceptor drum by a scraping blade before succeeding electric charges are accumulated.
Incidentally, though torque transmitted through a driving system for rotating a photoreceptor drum is mostly constant, resistance of a scraping blade which comes in contact with an outer circumferential surface of the photoreceptor drum and scrapes toner off, for example, usually fluctuates irregularly. If this resistance increases, a rotating speed of the photoreceptor drum is low, while, if this resistance decreases, a rotating speed of the photoreceptor drum is high, thus, rotational fluctuation of the photoreceptor drum is intrinsically caused. When the rotational fluctuation is caused on the photoreceptor drum, an image is not formed uniformly, causing a fear of a decline of image quality.
For preventing rotational fluctuation of this kind, a fly wheel having the great moment of inertia is provided to be coaxial with the photoreceptor drum. Due to the great moment of inertia,: this fly wheel can absorb rotational fluctuation of the photoreceptor drum to a certain extent/
However, it was found that rotational fluctuation is still caused occasionally on the photoreceptor, even when a fly wheel having the great moment of inertia is provided. A fly wheel, a shaft connected to the photoreceptor drum and gears in a driving system form a torsional vibration system. In the torsional vibration system of this kind, there exists a natural frequency. Therefore, if resistance of a scraping blade which comes in contact with an outer circumferential surface of the photoreceptor drum, for example, generates vibratory force to start vibration at a frequency which is close to a natural frequency of the torsional vibration system, the so-called resonance phenomenon is caused on the torsional vibration system, and great torsional vibration is generated on the fly wheel. The torsional vibration of this kind causes rotational fluctuation of the photoreceptor drum and thereby affects adversely on image forming.
On the contrary, even if the moment of inertia of the fly wheel is further increased, the natural frequency still exists and it rather moves toward the low frequency side, and transmission magnification is increased, resulting in another trouble that resonance phenomenon tends to be caused.
Further, although the changing of torque from a driving system under an electronic control in accordance with fluctuation of resistance of a scraping blade can be considered, the control mechanism needs to be complicated and high-performance motors and expensive electronic parts are necessary, which increases cost of an image forming apparatus.
In addition, not only for the image forming apparatus, various technologies have been used as a stabilizing technology for driving of a body of rotation. For example, there is known a technology to arrange a damper for achieving stabilized driving of a motor. For example, Japanese TOKKAISHO No. 61-9156 discloses a damper for a stepping motor wherein a flange section and an inertia body both fixed on a motor shaft are combined together through an elastic member. However, since an elastic body is stuck to the flange section and an inertia body through adhesives or baking, it is not possible to change a position, the number and materials of the elastic body, and it is also impossible to change dimensions and materials of the flange sections and inertia bodies, resulting in less versatility and low degree of freedom in use. Further, even if the elastic bodies and inertia bodies are deteriorated, they can not be replaced, and a damper needs to be replaced totally. Since those with a conventional structure lack versatility as stated above, other types are necessary to be prepared in advance, which causes additional cost.
In view of the problems in the prior art, it is an object to provide a rotation stabilizing device which is versatile for use and has high degree of freedom and deters rotation fluctuation to stabilize the rotation, and a rotation driving mechanism, an image forming apparatus and an image reading apparatus all being equipped with the rotation stabilizing device.
Another object of the invention is to provide an image forming apparatus wherein the structure is simple, and rotational fluctuation of a body of rotation such as a photoreceptor drum can be deterred.
To attain the objects stated above, a rotation stabilizing device of the invention has therein a rotary member which rotates around the central rotation axis, an inertia member which is arranged at the position different from that for the rotary member in terms of the axial direction of the central rotation axis, and a connecting member which is provided with a viscoelastic member having viscosity and elasticity and connects the rotary member and the inertia member in a detachable manner through the viscoelastic member, and is characterized in that the connecting member is provided at the position which is away from the central rotation axis in the radial direction.
Owing to this rotation stabilizing device, fluctuation of rotating speed of the rotary member is controlled by vibration of the inertia member, and the viscoelastic member having viscosity and elasticity is deformed in accordance with vibration of the inertia member. Therefore, even in the case of generation of vibratory force that causes fluctuation of rotating speed on the rotary member, this fluctuation of rotating speed is controlled, and the rotary member can rotate stably. In addition, since the connecting member connects the rotary member and the inertia member in a detachable manner, it is easy to replace the viscoelastic member, the rotary member and the inertia member, combination of each member is more flexible, adjustment for stabilizing rotation is easier, thus, it is possible to realize a rotation stabilizing device having versatility in use and high degree of freedom. It is also possible to realize a rotation stabilizing device having construction which is of low cost and is strongly-built because of simple structure.
When there is provided a rotary shaft which is fixed on the rotary member and rotates solidly with the rotary member, this rotary shaft can be connected with a rotary shaft of a motor, and thereby, the rotation stabilizing device can be attached on the motor.
When the connecting member is equipped with an attaching member which attaches the viscoelastic member on the rotary member and on the inertia member, it is easy to attach the viscoelastic member.
When the attaching member is provided with a flange section which is formed solidly with the viscoelastic member, it is possible to attach the viscoelastic member on the rotary member and the inertia member. In this case, it is preferable to arrange so that the flange section of the attaching member may be interposed between the rotary member and the inertia member.
The attaching member can be arranged to be supported by a supporting member which is provided on at least one of the rotary member and the inertia member. In this case, it is preferable that the attaching member is fixed on the supporting member with screws or is fitted in the supporting member. It is also preferable that the attaching member is inserted into a through hole formed on the viscoelastic member to be supported with the supporting member.
Further, it is preferable that the rotary member is structured to be in a disc form, and the inertia member is structured to be in a disc form, and in this case, it is preferable that a diameter of the inertia member is greater than that of the rotary member. Incidentally, the disc form mentioned in the present specification means a form on the section obtained by cutting in the direction perpendicular to the central rotation axis, and it also includes those in a flat plate shape and a cylindrical shape.
It is preferable that a plurality of the connecting members are arranged, and in this case, it is preferable that the connecting members are arranged on a concentric circle of the central rotation axis to be provided on locations divided at regular intervals in the circumferential direction on the concentric circle.
A rotation driving mechanism of the invention has therein a rotary member which rotates around a central rotation axis, an inertia member which is arranged at the position that is different from that of the rotary member in the axial direction of the central rotation axis, and a connecting member which has a viscoelastic member having viscosity and elasticity and connects the rotary member with the inertia member in a detachable manner through the viscoelastic member, and is characterized in that a rotation stabilizing device wherein the connecting member is provided to be away from the central rotation axis in the radial direction, a rotation driving means, a rotary shaft which is rotated together with the rotary member by the rotation driving means and a rotation transmission mechanism connected with the rotary shaft are provided.
In this rotation driving mechanism, fluctuation of rotating speed of the rotary member is controlled by vibration of the inertia member and the viscoelastic member having viscosity and elasticity is deformed in accordance with vibration of the inertia member. Therefore, even when vibratory force that causes fluctuation of rotating speed is caused on the rotation driving means, this fluctuation of rotating speed is controlled, and the rotary member of the rotation stabilizing device can rotate stably. As a result, a rotary shaft can rotate stably, and thereby, stable rotation is transmitted from the rotary shaft. Since the connecting member of the rotation stabilizing device connects the rotary member with the inertia member on a detachable manner, it is easy to replace the viscoelastic member, the rotary member and the inertia member, each member can be combined freely, and appropriate adjustment for less vibration can be made easily in the rotation driving mechanism.
In this case, it is preferable that the rotation stabilizing device is further provided with a rotary shaft on the part of the rotation stabilizing device which is fixed on the rotary member to rotate solidly with the rotary member and is connected with the rotary shaft.
It is also possible that the rotation driving means is provided with a rotary drum, and the rotary member of the rotation stabilizing device is structured to be solid with the rotary drum. In this case, the inertia member is connected with the rotary drum through a viscoelastic member.
The rotation transmission mechanism can be provided with a toothed pulley connected with the rotary shaft, a toothed belt which engages with the toothed pulley, and with a toothed pulley which engages with the toothed belt provided on a driven portion. Further, the rotation transmission mechanism may also be provided with a first gear connected to the rotary shaft and with a second gear which is provided on the driven portion and engages with the first gear. Incidentally, in this case, it is also possible to arrange so that the pulley and the gear are made to be solid with the rotary member of the rotation stabilizing device.
It is further possible to make a stepping motor to serve as the rotation driving means.
An image forming apparatus of the invention is characterized to be provided with a rotation driving mechanism which has therein a rotary member which rotates around a central rotation axis, an inertia member which is arranged at the position that is different from that of the rotary member in the axial direction of the central rotation axis, and a connecting member which has a viscoelastic member having viscosity and elasticity and connects the rotary member with the inertia member in a detachable manner through the viscoelastic member, and is provided with a rotation stabilizing device wherein the connecting member is provided to be away from the central rotation axis in the radial direction, a rotation driving means, a rotary shaft which is rotated together with the rotary member by the rotation driving means, and with a rotation transmission mechanism connected with the rotary shaft, a body of rotation which is provided with an image carrier which carries an image formed by an image forming means, and with a fur brush cleaning unit which is driven by the rotation driving mechanism to rotate and cleans the body of rotation.
In the image forming apparatus, even when vibratory force that causes fluctuation of rotating speed is caused on the rotation driving means, this fluctuation of rotating speed is controlled, and the rotary member of the rotation stabilizing device can rotate stably. As a result, a rotary shaft can rotate stably, and thereby, stable rotation is transmitted from the rotary shaft. Therefore, the fur brush cleaning unit rotates stably, and the body of rotation can be cleaned firmly and uniformly.
Another image forming apparatus of the invention is characterized to be provided with a rotation driving mechanism which has therein a rotary member which rotates around a central rotation axis, an inertia member which is arranged at the position that is different from that of the rotary member in the axial direction of the central rotation axis, and a connecting member which has a viscoelastic member having viscosity and elasticity and connects the rotary member with the inertia member in a detachable manner through the viscoelastic member, and is provided with a rotation stabilizing device wherein the connecting member is provided to be away from the central rotation axis in the radial direction, a rotation driving means, a rotary shaft which is rotated together with the rotary member by the rotation driving means, and with a rotation transmission mechanism connected with the rotary shaft, a body of rotation which is provided with an image carrier which carries an image formed by an image forming means, and with a transfer roller or a transfer belt which is driven by the rotation driving mechanism to rotate and transfers an image carried by the image carrier onto a transfer sheet.
In the image forming apparatus, even when vibratory force that causes fluctuation of rotating speed is caused on the rotation driving means, this fluctuation of rotating speed is controlled, and the rotary member of the rotation stabilizing device can rotate stably. As a result, a rotary shaft can rotate stably, and thereby, stable rotation is transmitted from the rotary shaft. Therefore, the transfer roller rotates at the constant speed stably, or the transfer belt moves at the constant speed stably, thus, accuracy for the transfer of an image onto a transfer sheet is improved and images with high quality can be formed.
Further, an image forming apparatus of the invention is characterized to be provided with a rotation driving mechanism which has therein a rotary member which rotates around a central rotation axis, an inertia member which is arranged at the position that is different from that of the rotary member in the axial direction of the central rotation axis, and a connecting member which has a viscoelastic member having viscosity and elasticity and connects the rotary member with the inertia member in a detachable manner through the viscoelastic member, and is provided with a rotation stabilizing device wherein the connecting member is provided to be away from the central rotation axis in the radial direction, a rotation driving means, a rotary shaft which is. rotated together with the rotary member by the rotation driving means, and with a rotation transmission mechanism connected with the rotary shaft, and with an image reading means which reads images while being moved relatively to a document by a pulley driven by the rotation driving mechanism.
In the image reading means, even when vibratory force that causes fluctuation of rotating speed is caused on the rotation driving means, this fluctuation of rotating speed is controlled, and the rotary member of the rotation stabilizing device can rotate stably. As a result, a rotary shaft can rotate stably, and thereby, stable rotation is transmitted to the pulley from the rotary shaft. Therefore, a movement of the image reading means in the course of reading is stabilized, and reading accuracy is improved.
Further, when an image forming apparatus or an image reading apparatus is provided with a rotation driving mechanism equipped with the rotation stabilizing device, rotation can be stabilized on the rotating portions other than the foregoing.
Another image forming apparatus of the invention has therein a body of rotation equipped with an image carrier which carries an image formed by an image forming means and a body of vibration attached on the body of rotation through a body of attenuation having viscosity and elasticity, and it is characterized in that fluctuation of rotating speed of the body of rotation is deterred by vibration of the body of vibration, and the body of attenuation deforms in accordance with vibration of the body of vibration.
In an image forming apparatus of the invention, a body of rotation equipped with an image carrier which carries an image formed by an image forming means and a body of vibration attached on the body of rotation through a body of attenuation having viscosity and elasticity are provided, and fluctuation of rotating speed of the body of rotation is controlled by vibration of the body of vibration, and the body of attenuation deforms in accordance with vibration of the body of vibration. Therefore, even when the vibratory force causing fluctuation of rotating speed on the body of rotation is generated, this fluctuation of rotating speed is controlled by vibration of the body of vibration, and deformation of the body of attenuation having viscosity and elasticity caused by vibration of the body of vibration can transform the fluctuation of speed into heat for convergence of the speed fluctuation, which makes it possible to form an image with high image quality.
Further, if the body of rotation is composed of the image carrier and the first disc portion connected to the image carrier through a shaft, and if the body of vibration is composed of the second disc portion which is provided on the first disc portion through the body of attenuation, the fluctuation of rotating speed of the body of rotation can be reduced by the displacement of the second disc portion from the first disc portion, and deformation in terms of expansion and contraction of the body of attenuation having viscosity and elasticity can deter the displacement of the second disc portion.
In addition, if torsional natural frequency F1 obtained from a spring constant of the body of attenuation and from the moment of inertia of the second disc portion, and torsional natural frequency F2 obtained from a compound spring constant of the shaft connecting the driving system for driving the body of rotation with the first disc portion and from the moment of inertia of the body of rotation, are made to satisfy the following expressions,
0.5xc3x97F2xe2x89xa6F1xe2x89xa62xc3x97F2
an attenuation effect by the so-called dynamic damper is exhibited, and thereby, the rotational fluctuation of the body of rotation can be deterred more effectively.
In this case, if the moment of inertia of the second disc portion is set to the value which is 20% or more of the moment of inertia of the body of rotation (more preferable is a value of 30%-120%), it is possible to raise further the effect of attenuation by the dynamic damper.
If the attenuation characteristic of the body of attenuation is made to be the characteristic expressed by the following expression,
Loss factor tan xcex4xe2x89xa70.05.
The attenuation effect can further be enhanced.
If natural frequency f=(1/2xcfx80)xc2x7{square root over ((K1/I2))} expressed by spring constant K1 of the body of attenuation and by moment of inertia I2 of the body of vibration is set to be smaller than the rotational frequency of the motor that drives the body of rotation and the engagement frequency of the gear that drives the body of rotation, it is possible to prevent resonance of the body of vibration, and thereby to deter the fluctuation of the body of rotation.
On the other hand, even when natural frequency f=(1/2xcfx80)xc2x7{square root over ((K1/I2))} expressed by spring constant K1 of the body of attenuation and by moment of inertia I2 of the body of vibration is set between the rotational frequency of the motor that drives the body of rotation and the engagement frequency of the gear that drives the body of rotation, it is possible to prevent resonance of the body of vibration, and thereby to deter the fluctuation of rotation speed of the body of rotation.